A hermetic seal terminal is formed by hermetically sealing a lead via glass in an insertion hole of an eyelet or metal outer ring and used in supplying current to an electrical device or an electrical element enclosed in a hermetic seal package and in leading a signal out of the electrical device or the electrical element. For example, as disclosed in Japanese Patent Laying-Open No. 2008-258100 (Patent Literature 1), a hermetic seal terminal for a compressor such as a refrigerator and an air conditioner is provided with a metal outer ring which includes a top plate portion, a cylindrical portion extending downward from the outer circumferential edge of the top plate portion, a flange portion flaring obliquely outward from the lower end of the cylindrical portion, and three small cylindrical portions which form lead sealing holes extending inward from the top plate portion. Further, a lead is hermetically sealed via sealing glass in each of the lead sealing holes of the metal outer ring.
For instance, in recent years, with the aims of preventing global warming and reducing environmental burdens, there are growing moves to switch from refrigerants such as HFC134a, which are based on replacement compounds for chlorofluorocarbons and conventionally used in compressors, to natural refrigerants such as carbon dioxide, which place less burden on the environment. Although carbon has always occurred in nature and has a minor impact on global warming, its application to compressors such as an air conditioner causes an approximately ten times higher internal pressure than application of HFC134a causes. Accordingly, the requirements for mechanical strength of hermetic seal terminals used for environment-friendly compressors are getting stricter. As such, there have been an increasing number of cases recently where hermetic seal terminals are required to be used in a harsher usage environment than expected. In a case of a compressor using the natural refrigerant described in the example above, the internal pressure reaches 10 MPa or higher. Conventionally, a hermetic seal terminal required to resists such high pressure needs special measures such as a structure using a special metal material for a metal outer ring and a lead, as disclosed in Japanese Patent Laying-Open No. 59-141179 (Patent Literature 2).